Electronic organ with plural master oscillators and plural vibrato oscillators for each note

ABSTRACT

An electronic organ having means for improving the musical quality of the notes produced by producing a number of parallel electrical signals having vibrato modulations which are mutually uncorrelated in frequency and/or phase. These signals are intermodulated to provide an output signal in which the components drift in and out of phase to produce a vibrato effect which resembles a conventional reeded or stringed instrument. The vibrator modulations can be provided either by low frequency oscillators operating on master oscillators (or tone generators) or by modulating a carrier frequency with a tone signal and using one sideband of the modulated signal thus produced to modulate a second carrier frequency signal. The difference in the frequencies of the two carrier frequency oscillators controls a frequency shift of the original tone signal and this difference can be controlled by a vibrato oscillator of suitable frequency.

United States Patent 1191 1111 3,847,050

Freeman Nov. 12, 1974 15 1 ELECTRONIC ORGAN WITH PLURAL 3.267.199 8 19 6 Hurvitz 84/125 MASTER OSCILLATORS AND PLURAL :ggg gw z mg I VIBRATO OSCILLATORS FOR EACH NOTE 3,413,403 1 H1968 Jacob 84/125 [75] Inventor: Kenneth Freeman, Sheldon, 3.440.325 4/1969 Schwartz et a1, 84/].25 E land 3,479,440 11/1969 Martin et a1. 84/125 I 3,516,318 6/1970 Wayne 84/101 [73] Ass1gnee: Audio Synthes1sers Limited,North Harron Mlddlesex England Primary ExaminerStephen J. Tomsky [22] Filed: July 26, 1971 Assistant Examiner-Stanley .1. Witkowski [21] pp No 166 116 Attorney, Agent, or FirmNorris & Bateman [30] Foreign Application Priority Data [57] ABSTRACT I Aug 26 1970 Great Britain 036/70 An electronic organ having means for improving the musical quality of the notes produced by producing a 52 us. 01 84/1.25 331/47 331/178 umber of Parallel filecmcal Signals having Vibmm 511 1111. C1. 61011 1/04 modulations which are mutually uncorrelmed [58] Field 611 Search 84/].01, 1.24, 1.25, DIG. 4. quency and/O I These l 84/122. 331/106 178 4649. 332/16 R 17 modulated to provlde an output slgnal 1n wh1ch the i 27 ii'zf 1 components drift in and out of phase to produce 21 vibrato effect which resembles a conventional reeded or [56] References Cited stringed instrument. The vibrator modulations can be provided either by low frequency oscillators operating UNITED STATES PATENTS on master oscillators (or tone generators) or by modu- 1,719,052 7/1929 Green 332/41 lating a Carrier frequency with a tone Signal and using 3 g t 2 one sideband of the modulated signal thus produced ,3 41959 gzi to modulate a second carrier frequency signal. The 3 E5 9/1959 Hanert 84/l'24 difference in the frequencies of the two carrier fre- 2Z920I284 1/1960 666 4551111 IB X quency oscillators controls a frequency shift of the 3,004,459 10 1961 Jones 84 1.01 origina tone Signal and this difference can be 3.007.36l 11/1961 Wayne 84/101 trolled by a vibrato oscillator of suitable frequency. 3,160,695 12/1-964 B0nham.... 84/125 3,255,297 6 1966 Long 84/125 14 Clalms, 2 Drawmg Figures i i i 15 76 i //0 /4a I l j MASTER FREQUENCY E OSCILLATOR DIVIDER Z 18 -/2- /lb /4b I9 OMS VIBRATO MASTER FREQUENCY I 27 OSCILLATOR OSCILLATOR DIVIDER Na 2:8 92 /3 //c -/4c 2' Q Q I VIBRATO MASTER FREQUENCY OSCILLATOR OSCILLATOR DIVIDER i) 22 FE; 1 1 24 PM? 11 I CTAVE$ 25 OUTPUT 0F 2? I ONE NOTE 27 3.

ELECTRON/C SWITCHING CIRCUIT RY This invention relates to electronic organs, and :particularly to electronic organs provided with means for obtaining a tremolo or vibrato effect on the notes produced by the organ.

Known electronic organs have individual master oscillators or tone generators of stabilised frequency for v producing different notes upon depression of respective keys. For example there may be 12 such tone generators for producing the 12 notes of a chromatic scale of the upper octave of the instrument, the notes of the lower octaves being obtained by suitable frequency division.

The tremolo effect in such electronic organs is achieved by applying a small frequency modulation at low frequency, typically of the order of six cycles per second, to the generated oscillations. This modulation is termed a vibrato oscillation.

In such known electronic organs, however, the nominal frequency of any one note is constant, or at least bears a constant relation to adjacent notes on the organ keyboard, each note being derived from a common master oscillator. This leads to a lack of musical colour in the notes produced as compared with notes derived from ordinary reeded or stringed instruments.

According to the present invention there is provided an electronic organ having a number of keys for producing different musical notes, each of the keys controlling the operation of a network comprising at least two oscillators, the frequency of each of the said oscillators being modulated by respective vibrato oscillators of mutually uncorrelated frequency and/or phase and the outputs of the said two oscillators being combined in the output electrical signal from the said network to produce a. tone which displays a random variation. Since the random variation is derived from two independent modulating sources, the resultant variation of tone is not monochromatic, and approaches the randomness of a conventional reeded or stringed instrument.

Preferably the frequencies of the respective oscilla tors are substantially the same and represent the musical note to be produced by the said network. The mutually uncorrelated modulation of the tone oscillators by the vibrato oscillators causes the frequencies of the tone oscillations to vary over small ranges around their nominal frequencies, independently of each other, and in an uncorrelated or incoherent manner. The result is that the oscillators tend to drift in a random manner in and out of phase with each other. I

In a preferred embodiment of the invention three tone oscillators and two respective vibrato oscillators are provided, the vibrato oscillators operating on two of the tone oscillators, the further oscillator producing an output signal at a substantially constant frequency at the nominal frequency of the two said oscillators. The resultant tone then resembles that of a multiplicity of stringed instruments or of a chorus, with subtle random variations about a mean frequency.

The vibrato oscillators are preferably free-running, ensuring that they have no phase correlation with each other.

The electronic organ according to the invention may be provided with other circuits in a known manner for LII 2 controlling, for example, the attack and decay of individual tones and for producing special echo effects.

Typically the frequency modulation of each tone oscillator is over a band-width of a fewcycles per second at a modulation frequency of the order of three to six cycles per second.

In an alternative embodiment the said oscillators are carrier frequency oscillators and the output from the said oscillators is also modulated by at least one side band of a modulated signal comprising the output from further respective carrier frequency oscillators modulated with an electrical signal representing the musical note to be produced.

Preferably the modulation of the said carrier frequency oscillators by the vibrato oscillators is effective to introduce a sinusoidal variation in the frequency thereof, although various other waveforms could be used.

It is preferred that the circuit also includes means for suppressing at least the carrier frequency of the said modulated signal, alternatively the said means may be effective to suppress the carrier frequency and one side band of the said modulated signal.

In a preferred embodiment the modulation of the said carrier frequency oscillators by the vibrato oscillators is effected with respect to the said further carrier frequency oscillators such that the vibrato oscillators control the difference between the frequencies of the said carrier frequency oscillators and the further carrier frequency oscillators. It is this difference that causes the shift in frequency of the components ofthe original electrical signal representing the musical note to be produced and thus the vibrato effects which when intermodulated with uncorrelated vibrato oscillations on a similar signal produce the subtle random variations to obtain the result desired.

According to another aspect of the present invention there is provided an electronic organ having a number of keys for producing different musical notes, each of the keys controlling the operation of a network comprising at least one oscillator for producing an electrical tone signal representing the musical note to be produced, means for modulating a first carrier signal with the said electrical tone signal to produce a modulated signal, means for suppressing the carrier frequency of the modulated signal and for modulating a second carrier signal with at least one sideband of the modulated signal, and means for varying the difference between the frequencies of the first and second carrier signals at a controlled rate whereby the frequencies of the components of the electrical tone signal are varied.

Preferably the means for varying the difference between the frequencies of the first and second carrier signals is operative to vary the said difference periodically at a given low frequency to produce a vibrato effect on the musical note produced. In a preferred embodiment the means for varying the difference between the frequencies of the first and second carrier signals is operative to vary the said difference sinusoidally. In this way the vibrato effect achieved will vary sinusoidally in a manner similar to known vibrato effects; however, with the present invention it is possible for various different vibrato signal waveforms to be used.

As mentioned above the first carrier signal alone may be suppressed or, alternatively, the means for suppressing the said first carrier frequency of the said modulated signal may operate to also suppress one sideband of the said modulated signal.

Similarly the difference between the frequencies of the first and second carrier signals may be varied by varying the frequency of the first carrier signal while maintaining the frequency of the second carrier signal substantially constant or alternatively may be varied by varying the frequency of the second carrier signal while maintaining the frequency of the first carrier signal substantially constant.

Two embodiments of the invention will now be more particularly described, by way of example, with reference to the accompanying drawings, in which:

FIG. 1 is a block schematic diagram illustrating one embodiment of the circuits for producing one note over a range of six octaves; and

FIG. 2 is a block schematic diagram illustrating a second embodiment of the circuits for producing a single note over a frequency range of six octaves.

Referring now to FIG. 1 there are shown three master oscillators 11a, 11b and 110. The master oscillators are identical and each is stabilised to produce an output electrical signal at a given frequency which represents themusical note to, be produced. The two master oscillators 11b and Home coupled to the outputs of two vibrato oscillators 12 and 13 respectively. The outputs from each of the master oscillators are fed to respective frequency dividers 14a, 14b, 14c the output from the master oscillator 11a being coupled to a frequency divider 14a, the output from the master oscillator 11b being coupled to the frequency divider 14b and the output from'the master oscillator 11c being coupled to the frequency divider 14c. Each frequency divider has six outputs along each ofwhich an electrical output signal representing the given note but on six different octaves is transferred via a waveform shaping device 15 in each line to a respective common octave line 16, 17, 18, 19, or 21. For example, the electrical signals representing a note on, say, the upper octave of the instrument are each fed to the common line- 16 by means of which they are led to a keyboard and switching control device 22 Similarly the signals representing each of the five lower octaves are fed via common lines to the keyboard and switching'control devices-23, 24, 25, 26 and 27 associatedthe'rewith In use of the instrument the oscillators are operating continuously: when one of the six notes produced from the oscillators 11 is to be played an appropriate key, for example a key associated with .the switching and control circuit 22, 23, 24, 25, 26, or 27 is depressed thereby connecting the outputs of the frequency dividers 14a, 14b, and 140 via the selected common line 16, 17, l8, 19, 20 or 21 to an audio transducer (not shown) of the instrumenLThe outputs from the master oscillators 11b and 110 are modulated, of course, by the outputs from the vibrato oscillators 12 and 13 respectively and accordingly these vary independently about their nominal frequency. The output from the master oscillator 11a is maintained substantially constant at the nominal frequency of the oscillators 11b and 110. The three oscillators thereby produce through the frequency device 14a, 14b, 14c a note which has independently varying components which drift in and out of the phase with each other to produce an accoustic effect which more nearly represents that which would be produced by a'conventional stringed or reeded instrument or by a chorus.

Referring now to FIG. 2 there is shown an alternative circuit for achieving the vibrato effect by means of which the subtle random variations about a mean frequency of the output electrical signal representing any one note can be achieved. In, FIG. 2 like reference numerals represent corresponding components of the circuit shown in FIG. 1. In the embodiment of FIG. 2 there is provided a single master oscillator or tone gen erator 11 which provides an output signal representing the note to be produced. The output signal from the master oscillator 11 is provided on three lines 29-and each connected to respective modulator'ci rcuits 35 arranged to modulate the output signal from one of three carrier frequency oscillators 28. In detail, the output signal from the master oscillator 11 which is fed along line 29a is passed to modulator 35a and modulates the carrier frequency signal from oscillator-28a, the output signal from the master oscillator which is fed along line 29b is passed to modulator 35b and modulates the output carrier frequency signal oscillator 28b, and the out-. put from the master oscillator which is fed along line 29c is passed to modulator 35c and modulates the output carrier signal from the oscillator 28c.

The modulated signals are passed along lines 30 to respective suppression circuits 31 where either the carrier frequency or the carrier frequency and one sideband are suppressed, and the sideband or sidebands of the modulated signal which form theoutput from the suppression circuits 31 are fed to respective modulator circuits 36 to modulate second carrier frequency signals from respective second carrier frequency-oscilla-- tors 32. The carrier oscillators'28 and 32 are connected in pairs to respecting control signal generators 33, that is the control signal generator 33a is connected to carrier frequency oscillators 28a and 32a, the control signal generator 33b is connected to carrier frequency oscillators 28b and 32b, and the control signal generator 33c is connected to the carrier frequency oscillators 28c and 32c. Each control signal generator 33 operates to vary the difference between the output frequencies of the carrier signal oscillators 28 and 32 either by maintaining one of the outputs from the control signal generator 33 constant and varying the frequency of the other or by varying the frequencies of both so that the components of the original tone signal in the modulated signal output from .the circuits 32 are phase shifted independence qnthe voltage of the generators 33. In this way each output signal is frequency modulated in dependence on the voltage of the generators The generators 33 produce a low frequency vibrato signal so that each output signal of the line 3411,3412, 340 is frequency modulated by this signal. The generators 33 are arranged to be entirely independent of each other, the outputs on the lines 34a, 34b and 340 are not linked in phase or frequency so that the inputs to the three frequency dividers 14 are thus in the same state as the inputs to, the frequency dividers 14 of FIG. 1,

that is, each input experiences small independent variations abouta mean frequency and the variations are effectively random so that the combined noteswhen re,- produced by an accoustic transducer (not shown) represent a conventional'stringed or reeded instrument, or a chorus by having subtle'random variations about the mean frequency.

I claim:

l. in an electronic organ having a number of keys for producing different musical notes, a network producing each note comprising at least two master oscillators, at least two vibrato oscillators, said vibrato oscillators each being connected for modulating the frequency of a respective master oscillator, the said vibrato oscillators operating at mutually uncorrelated frequency and/or phase, and means operative upon actuation of each of said keys for combining the outputs of the said two master oscillators thereby forming an output electrical signal from said network to produce a musical note which displays a random variation.

2. The electronic organ of claim 1 wherein both said master oscillators produce output electrical signals substantially representing the musical note produced by said network.

3. The electronic organ of claim 1 wherein said network includes at least one further master oscillator producing an output signal at a substantially constant frequency at the nominal frequency of said two master oscillators, said output signal from said further oscillator being combined with the outputs of said other two master oscillators.

4. The electronic organ of claim 1 wherein said vibrato oscillators are free-running oscillators.

5. in an electronic organ having a number of keys for' producing different musical notes,

a network producing each note comprising at least two first carrier frequency oscillators producing carrier frequency signals,

means modulating said carrier frequency signals to produce a modulated signal, said modulating means including oscillator means producing an electrical signal representing the note produced by said network,

at least two second carrier frequency oscillators, producing second carrier frequency signals, means modulating said second carrier frequency signals with at least one sideband of said modulated signal,

means controlling the frequency difference between respective pairs comprising one said first carrier frequency oscillator and one said second carrier frequency oscillator, said controlling means operating at mutually uncorrelated phase and/or frequency, and

means combining the modulated outputs of said two second carrier frequency oscillators and forming the output electrical signal from said network to produce a musical note which displays a small random variation.

6. The electronic organ of claim 5 wherein said means controlling the difference between the frequencies of said first and second carrier frequency oscillators operates tointroduce a sinusoidal variation in the difference between the frequencies thereof.

7. The electronic organ of claim 5 wherein there are provided means suppressing at least said carrier frequency of said modulated signal.

8. The electronic organ of claim 7 wherein there are provided means suppressing both said carrier frequency and one side band of said modulated signal.

9. In an electronic organ having a number of keys for producing different musical notes,

a network comprising at least one oscillator producing an electrical tone signal representing the musical note to be produced,

first carrier frequency oscillator means, producing a first carrier signal,

means modulating said first carrier signal with said electrical tone signal to produce a modulated signal,

means suppressing the carrier frequency of said modulated signal,

second carrier frequency oscillator means producing a second carrier frequency signal,

means modulating said second carrier frequency signal with at least one sideband of said modulated signal, and

means varying the difference between the frequencies of said first and second carrier frequency oscillators at a controlled rate whereby the frequencies of the components of said electrical tone signal are varied.

10. The electronic organ of claim 9 wherein said means varying said difference between the frequencies of said first and second carrier frequency oscillatorsis operative to vary said difference periodically at a given low frequency to produce a vibrato effect on the musical note produced.

11. The electronic organ of claim 10 wherein said means varying said difference between said frequencies of said first and second carrier frequency oscillators is operative to vary said difference sinusoidally.

12. The electronic organ of claim 9 wherein said means suppressing said carrier frequency of said modulated signal also operates to suppress one sideband of said modulated signal.

13. The electronic organ of claim 9 wherein said difference between said frequencies of said first and second carrier frequency oscillators is varied by varying the frequency of said first carrier frequency oscillator while maintaining the frequency of said second carrier frequency oscillator substantially constant.

14. The electronic organ of claim 9 wherein said difference between said frequencies of said first and second carrier frequency oscillators is varied by varying said frequency of said second carrier frequency oscillator while maintaining the frequency of said first carrier frequency oscillator substantially constant. 

1. In an electronic organ having a number of keys for producing different musical notes, a network producing each note comprising at least two master oscillators, at least two vibrato oscillators, said vibrato oscillators each being connected for modulating the frequency of a respective master oscillator, the said vibrato oscillators operating at mutually uncorrelated frequency and/or phase, and means operative upon actuation of each of said keys for combining the outputs of the said two master oscillators thereby forming an output electrical signal from said network to produce a musical note which displays a random variation.
 2. The electronic organ of claim 1 wherein both said master oscillators produce output electrical signals substantially representing the musical note produced by said network.
 3. The electronic organ of claim 1 wherein said network includes at least one further master oscillator producing an output signal at a substantially constant frequency at the nominal frequency of said two master oscillators, said output signal from said further oscillator being combined with the outputs of said other two master oscillators.
 4. The electronic organ of claim 1 wherein said vibrato oscillators are free-running oscillators.
 5. In an electronic organ having a number of keys for producing different musical notes, a network producing each note comprising at least two first carrier frequency oscillators producing carrier frequency signals, means modulating said carrier frequency signals to produce a modulated signal, said modulating means including oscillator means producing an electrical signal representing the note produced by said network, at least two second carrier frequency oscillators, producing second carrier frequency signals, means modulating said second carrier frequency signals with at least one sideband of said modulated signal, means controlling the frequency difference between respective pairs comprising one said first carrier frequency oscillator and one said second carrier frequency oscillator, said controlling means operating at mutually uncorrelated phase and/or frequency, and means combining the modulated outputs of said two second carrier frequency oscillators and forming the output electrical signal from said network to produce a musical note which displays a small random variation.
 6. The electronic organ of claim 5 wherein said means controlling the difference between the frequencies of said first and second carrier frequency oscillators operates to introduce a sinusoidal variation in the difference between the frequencies thereof.
 7. The electronic organ of claim 5 wherein there are provided means suppressing at least said carrier frequency of said modulated signal.
 8. The electronic organ of claim 7 wherein there are provided means suppressing both said carrier frequency and one side band of said modulated signal.
 9. In an electronic organ having a number of keys for producing different musical notes, a network comprising at least one oscillator producing an electrical tone signal representing the musical note to be produced, first carrier frequency oscillator means, producing a first carrier signal, means modulating said first carrier signal with said electrical tone signal to produce a modulated signal, means suppressing the carrier frequency of said modulated signal, second carrier frequency oscillator means producing a second carrier frequency signal, means modulating said second carrier frequency signal with at least one sideband of said modulated signal, and means varying the difference between the frequencies of said first and second carrier frequency oscillators at a controlled rate whereby the frequencies of the components of said electrical tone signal are varied.
 10. The electronic organ of claim 9 wherein said means varying said difference between the frequencies of said first and second carrier frequency oscillators is operative to vary said difference periodically at a given low frequeNcy to produce a vibrato effect on the musical note produced.
 11. The electronic organ of claim 10 wherein said means varying said difference between said frequencies of said first and second carrier frequency oscillators is operative to vary said difference sinusoidally.
 12. The electronic organ of claim 9 wherein said means suppressing said carrier frequency of said modulated signal also operates to suppress one sideband of said modulated signal.
 13. The electronic organ of claim 9 wherein said difference between said frequencies of said first and second carrier frequency oscillators is varied by varying the frequency of said first carrier frequency oscillator while maintaining the frequency of said second carrier frequency oscillator substantially constant.
 14. The electronic organ of claim 9 wherein said difference between said frequencies of said first and second carrier frequency oscillators is varied by varying said frequency of said second carrier frequency oscillator while maintaining the frequency of said first carrier frequency oscillator substantially constant. 